1. Field of the Invention
This invention relates to a robot control apparatus in which robot control conditions are set by a monitor program described in robot language.
2. Description of the Related Art
In order for a predetermined task to be performed automatically using a robot, it is necessary that the robot first be taught a series of activities such as grasping of an object, moving the object and placing the object at a predetermined position. Teaching operations of this kind are generally done on the user side. In such case, the operation conforming to the taught instructions is performed based on a user program stored within a robot control apparatus.
FIGS. 6(a) and (b) respectively illustrate a user program for teaching a robot a series of operations, and the operating procedure of the robot based on this user program. Programs P0 through P7 shown in FIG. 6(a) are described in a predetermined robot language. When the robot is made to perform the series of operations shown in FIG. 6(b), the user program is started on the robot control apparatus side by a system program to output motion commands for the robot.
In the above-mentioned system program, it is required that the status of the robot be monitored at all times and that the operations be performed under predetermined conditions. This status output function required for the robot control apparatus is described in the form of specific instructions for, e.g., generating a predetermined output when the robot is in position, generating an output when an arm is at a fully retracted position, and halting robot motion when a safety rack is open. Since the robot must be monitored at all times after the introduction of power, the program for implementing this status output function cannot be described in a robot language the same as that of the user program run by being started from the system program. In order to perform an operation of this type, a robot language having a function referred to as a "monitor" function is available, but the robot operation cannot be monitored at all times by a program described in this language.
More specifically, since an operation requiring constant monitoring must generally be incorporated in the system program, the output of robot status in the conventional robot control apparatus is monitored at all times by the system program. However, the entire system program is stored beforehand in a read-only memory (ROM) and is designed to be fixed in the robot control apparatus. As a result, the user cannot set and modify the program at will.
Accordingly, when it is desired to modify the present contents of a robot operation or add another operation to the present operation, the system program inside the ROM must be altered. A problem that arises is that in order to accomplish this, the user must replace the read-only memory (ROM) on each such occasion.